Nausea and vomiting occur in up to 80% of normal pregnancies. Hyperemesis gravidarum, resulting in dehydration and ketonuria, is a more severe, disabling and potentially life threatening condition affecting up to 1.5% of pregnancies. Treatment is supportive with intravenous rehydration, antiemetics and correction of vitamin deficiency to minimize complications. There are good safety data to support the use of antihistamines, phenothiazines and metoclopromide in hyperemesis gravidarum, though trials of efficacy are lacking and there is little evidence on which to chose the optimum therapy. This review discusses the diagnosis and management of hyperemesis gravidarum and the prevention, recognition and treatment of the serious complications of Wernicke encephalopathy, osmotic demyelination syndrome and thromboembolism.